Current-transmitting instrument.



C. D. LANNING.

CURRENT TNANSMITTING INSTRUMENT.

APPLICATION FILED JUNE 6, 1907.

1,073,692. Patented sept.23,1913.

2 SHEETS-SHEET 1.

Iig-1 44 40 6'/ Hilf/4 /znesses fnvenor C. D. LANNING.

CURRENT TRANSMITTING INSTRUMENT.

APPLICATION FILED JUNE 5, 1907.

Patented Sept. 23, 1913.

2 SHEETS-SHEET 2.

DD..- DT? 2 ...WM5 f .n M @t y Z CHARLES LD. LANNNG, CF BOSTON, MASSACHUSETTS.

CURREN`T-TR 'ITTING NSTRUMENT.

Specifica/tion of Letters latent.

Application tiled June 5, w07.

Patented Sept. 1913.

Serial No. 377,313.

To all wlw/m, t ym n.3/ concern Ee it known that l, CHARLES l); ltmNiNo,

a ritiaen ot' the Uniti-wl States. ri-rsidint;` in l Boston, in the count): ot Sutl'olk and State of t Massachusetts, hare invented an Improvement in Current-Transmitting .instrumenten of which the following desieriptitm, in eonnection with the accompanyingdrawings, is a speoiiieation, like letters on the drawings repretseriting like parte.

My invention relates to telephone inStru- .ments for transmitting electrical current and more part-ieularly though not exelu- Sively, to repeating instruments oil the granular microphone type for repeating, relaying, or reint'oreing telepl'mne currents.

This invention aims, generally, to improve instrumente of this type by providin;l simple and ettective ine-.me for preveeting` the packing of grannies between the electrodes et' the microphone, said iria-cking heine; an inherent detect of instrui'nents empl(yingl granular carbon and impairing and diminisl'iing the etlieienoy thereof. The allieve.,

hovever, with other features and ohj ot my invention will he best understood and appreciated by reference ti; Lie, 't'ollor.'ing de eoription, when taken in eonneetion with the accompanying drawings, el a repeating),` instrument embodying one forinf'ot my in vention. and selected fer iuirposei,l of illustration,.its scope being more partieularl \Y pointed out in the appended elaiuas. n

In the drawings;Figure l, is n plan View of a repeating instrument einlnutlring one forni of my invention; Fig. f2, a. Side eleva `tion of the Same, partially in vertical see- Fig. l; Fig'. 3. an end a 'tion on the line 2HE, elevation, from the right Fig. l; Fig. detail of the arm for turningl the microphone; Fig. 4, a diagrammatic representation of a telephone circuit embodyingmy invention Vto represent the switch meehanism employed for rendering` the autipaeking mechanism inoperative upon the establish ment ot' through Connections. l? 5 and t3, are siinilar views ri modihed forms of 'witch meel'urnisni that may he substituted 'for that shown in Fig. 't; and Fig. T. a tele-- phone system showingi a modified arrange- 'ment el repeatingl eireuits to which retereneewil-l he made. I ,A

Referring to the drawings and more partienlarlyto the selected embodiment illustratod in Figs. l to 3, there is shown a. repea ting instrument for repeatiner the current undulations oft" a main tine eireuit or from one nireuit to a. second circuit. in the circuit connections ot' this type ol apparatus are well known to those skilled in the art, the saine are not: herein Speeitieally shown and may he but briefly described.

In the present instante, one side, a, of the main line eirouit, Fig. 4, preferably a metallic circuit7 is r'ieriallir connected to the binding posts l, 1', Fig. l, which as herein shown, are connected with the energizingr coils f2 ot a reve ingf magnet 3, while the other eide` '6, of the main line Circuit, through which the current undulations of the first are repeated or transmitted, with intensification to the distant listening or re oeiring letatio'n, is connected in Series with the bindingf posts il, 4', the latter being in series with the terminals o't` the finely wound eeeo-ntflaiv of an induction coil 5. The primary `winding,r ot'i this eoil is in what in herein denominated the repeating eireuit, e, and connected to a third set ot liindinfgs posts, (t, ti', the latter being' in Series with a suitable source ol" elef'trieal energy, sueh as a battery 7, lt`ig. 1, the repeating eireuilt, f'. in paesino' from the induction coil to the binding poet, t, including the variable resistant-e transmitting instrument or inieropl'iomx S, hy means oit' tlenihle eonduetors El, 9. attached ress'peetirely to the movable and fixed @leetrodes thereof.

Couride ingr lire-:t the rer-eiriug f-fleetromagnet 3. the latter so eonetrueted and operativelv related to the mierophone as to traamnit magnetic Variatioimy to the repeatine` eireuit with a minin'iizcation ot the waste et' ettorn l`o produce as et'teetire u magnetie tield as is poesihle, Vfrom the variable .line energy ol the main line eil-Cuit'. said magnet is provided with an armature l0. whieh is eltfsely aeszoeiated with the were ot' the magnet. so ne to provide a substantially complete magneticy eireuit only interrulirted hv Such au air frat) at: is effzweutial to iermit` Suitable vibratorv movement of the armature. its herein shown, Said magnet, 53, is pre ferahly o't the nian'netized horse lQhoe type commonly emi'iloyed in telephone inetruments, the arme; ot the magnet: reeeivingthe line magnet-ization eoile` L), which are plane-,d at the extreme end thereof, so that prac v rent undulations of the telephone line.

The magnet is adjustable longitiidina-lly or toward and from the armature and is v. secured in desired adjustment and maintained in horizontal position upon a suitable uarirfht suiaort l1 Fic: 2 b r means of a preferably non-magnetic clamping plate 12,

land clamping screw, 13, said support 1l being suitably secured to the bast-:board 14 of the instrument.

, To provide an armature of relatively loivv magnetic reluctance,y the lat-ler is preferably of block form, herein preferably dist shaped and preferably laminated to'elnnniato eddy currents, the Vdimensions of the armature being such as to provide asuitable path for the magnetic flux of the magnet and an armature-electrodeV of relatively light Weight and low inertia. As shoivn in Figs. I andl 2, this armature is normally in close I'nagnetic relation to the magnet and in a po-sition to be most effectively operated thereby. As thus constructed, a highly ellicient armature is provided that responds readily to the energization current lofthe main line circuit and is effective to produce the best resultsin actuating the microphone to which it is operatively connected.

In the present instance, the microphone employed is of the granular carbon .type` such for example, as t-he solid back microphone Vtransmitter shown'in the drawings, Figs. l and 2. As is ivell known, this type of microphone ordinarily comprises a suit` able cylindrical casing 1f?, Fig. 2, lWithin which is what istermed the resistance but-` ton, As herein shown, this' resistancebutton comprises a relatively fixed or stationary carbon electrode 1G at the bottom of the customary button receiving or carbon chamH ber with which micropho .es of this type are provided, 'a vibratory or movable carbon electrode 17 at the outer end of said chamber, and an intermediate body of finely divided or granular conducting material, such as carbon granules 18, which are confined in said chamber between said electrodes. The stationary electrode is secured to the microphone casing and the movable electrode is -connected with the described armature of the electromagnet, so that it moves therewith and vibrates toward and connected block 28 relativer);

from the fixed electrode and thereby varies the resistance of the intermediate body of the granular carbon in a manner Well understood.

For connecting the vibratory electrode of the microphone to the electromagnet armature, 10, any suitable means .may bel employed that will maintain it in definite relal tien to the ixed'electrode and permit suit-- able vibratory movement, tho-ugh I prefer the construction herein shown, wherein a light aluminum plate 19- is attached to the cuter surface of said movable electrode, said plate being mounted upon a light diaphragm 20, herein of mica, which is secured by its periphery to said casing by means of a suitable retaining and clamping rin@ 21. This diaphragm is centrally provided with an outwardly, projecting stem 22, Which is secured by an insulating collar 23 at its outer end to the back of the electrode armature.

.By this construction the `vibratory-electrode 17 is supported in operative relation to its coperatin0` stationary electrode 16 and the vibrator-y or microphonic movement, essential to the ctlicient operation of the microphone, is readily permitted, the said electrode having a plunger like movement l toward and from the electromagnet for varying the amount of air gap and to provide a suitable `transverse movement for centering the microphone with reference tothe line of magnetic pull produced by the magnet on its armature. To this end, the inner end of the casing is provided with a pro- Iiection 2- 1 Which is secured'in the forked end of a relatively massive revoluble shaft 25 by means'of a clamping screvr 26, said shaft being suitzitbly journaled in a pair of uprights 27 carried by ajbl'ock 28. This block is mounted to slide transversely in a supporting block 29 mounted for longitudinal adjust-ment between standards V30. The transverse adjust-ment of the inner block 28 is permitted by providing the block 29 with suitable ways A31, said adjustment being effected by means of a transverse adjustingv screw 32 in threaded engagement yWit-h ay block 28 and rotatably mounted at itsfends iro.

in said block 29 and providedwith a lock nut-32%.l ABy this construe om. the screw.- may be turned to produce n ement of the the carrying this type wherein grarmlar hlocli' 2t), so that it may he moved 'from one or the other Sido of the axis 0i the magnet to presenty the armature in denA l centr-.il oosition relative to the pole pieces oil 'f'ne magnet.

To secure longitudinal "liustnient o't' the. microphone, the hloch Q9 xongitvrl7 .tally threaded to receive. an adjusting,` screw 152%. The latter iS journalcd at 5% in the standards 8O of the hase hoard, and hy rotating' the screw, said. block may he moved towarlfl and from vthe magnet andisccurcd in any adjusted position hy means otl a lock nut .'55 upon the engaging thriads toi-med on the outer and reduced ond o't' the screw.

ln repeating` and relaying instruments of' rarhon is oni-- ployed, and to a lesser extent also in the ordinary g anular :arhon tansmitter, there is a tendency of the granules-a in the carbon cl'ian'iliier to pack, said packingl in'ipairing the resistance varying` l roperties ot the carbon naiss in resi'ionding to the `rehitive \i hrations of the electrodesI and ti-)rniinate the transmitting etiiciency ot' the inztrulnent. This packingi ot the carhon granules, a delect inherent in instruments ol this type, is principally duc to the zQ"ayitati m ot the ifranulij-n to thi liottoin otl the cai-hon chamher and the prceent invention provides suitahle means tor reSt-oring thegj'anules to their normal unpacked condition between the electrodes so zo; to render the instrunient more ellectii'e. To this end and in the present' 'iufltance ot my invention, the transmitter i, neriodically rotated successively to hi'inn` fun-li portions oit the rarhou ichamher in w-hicn the granules tend to pack to the top ot the instrun'ient, which ctlects di placement. lcoseningl, and rmiseipiel'lt unpacking; ot the granate-a.) therein' retmfincY them to their normal unpacked. looe. oondition.

Referring more particularly to Fig l. and the reyoluhle shai't` 25 which at its inner end euri-ics the microphone in provided interii'icdiatc Said upritlzls 2T with a rocking' arn'i 36. the huhl'icll cnil ot' which is leoeely mounted ou said shalt. The Sh: 'it hearing; surface oli this huh, howeier.I is prt vided with a longitudiiuilly extending notch il?, Figs. 3, 3 wedge shasxieil in cross` acction. ii-ranged in thie` notch in a plurality ot triction halls S8, which perinit `the arm to hc .urncd freely in one t irection. upward, Fig. fl, the hails j -j avitatinel toward the small end ot the notch, hut when itil outer end is swung downward produee a grippiiig action upon said shaft to causey the latter to turn with it. This arm is oscillated hack and 't'nrtli rwricdically, .no that the varhon granules in the carhon chamber ot the microphone are intermittently distributed or restored to their normal ,loose condition thus effectively preveiiting the packing thereof.

The shatt 25 in provided with a collar 2F which hears againstthe outer Sur't'aee of the lett upright, QT, Fig. ll, and the opposite end ot said sha't't extends beyond the right', upright 2T and is exti-riorly provided with a Sari-omitting still' coil :springil.) which if; interposed hctwcen the milled head ot said' -;lni;t't and a washer 25" also on said shaft and hearing; aeainot the outer tace ot' the right upright 2?. This lprin' Elf) normally maintains the hatt i5 in the position shown in .aaid llig. l, and preriaite any longitudinal movement ol' .said nhattor ot the microphone :ming when the arinature-electrode ot the latter is tibi-ated hy the action ot the eleetrotte magnet 3. liy this ar 'angeinent, the microphone is maintained in predetermined magnetic relation to the electromagiet While reroluhlc 1n=.`\'erncut thereot is freely permitted. 'l`o proridc suitable means for producing; thi1-` oscillating movement of the arm 36, l prefer: hl); proriifle a lo al circuit (l, liest hown in Fig. l. connected to the` hind tuti posts lttl and in which ifi a vertical electroinagnet -lt mounted upon said haseboard lt the magnet poles beingv in closeV association with a auitahlc armature il upon the 'tree end ot .said lever. 'the coils oi this n1agurtare energized hy a silitahle i-tource ot electrical cncrgi'y. .auch :1S a battery ft2 arranged in :series in naid local circuitv` and it will he ol'wiou-o as long' as the circuit is closed that the magnet will cause the depression' ot the outer end oi' said lever and hold it down upon lthe` magnet until the circuit is hri'iken. 'lhe armaturcd end ot said lever, Fig. 8, is normally maintained in elevated position by a coil Spring; Il!) connecting the same `to a suitable Standard tl upon the hase, et, said Spi-ingr y'chling' lo permit depri'ission ot' said arm when thc local circuit if; cloned and eleiatingg it when the circuit Vis broken. To open and close this local circuit periodically, no that the microphone may he intermitl.ir.. l rotated` said circuit is provided with current interrupting and closingr iii-aua1 which ohviously may he ot any suitable con Strut-tion, hut as herein showin comprise a suitable clot-lr wr-rl; l5, which causes the rcrolution of an outer circuit making and lli-calling wheel iii. the pcripln-ry ot which if. prmillcil with insulating and conducting ain-tacco t7` ltv. ln Suitable relation to the periphery of this; wheel` herein at one side tlm-cot, Fig. --l. i. a Snitahle contact pring ttl. one terminal ot the local circuitv heilig; ccnnectcd therewitlpaud the other to the nietallic or conductingl surfaces,l oi ,said wheel. in ol'icration, the rotation ot Said wheel, lu'innz the contact point oi' the spring;l into Successive contact with conducting 'and iiisulatinp; surfaces thereof. thereby respecA tircly opening and closing the lccal circuit to cause, through the electroinagiieti` action of the magnet 40 upon .its armature 41, the

periodic .oscillation of the arm 36 and the consequentperiodic turning movement of the microphone. The relative number of insulating and conduct-ing surfaces upon the .periphery of said wheel may obviously be 5 for breaking the local circuit upon the establishment of through connections. To this end and referring to Fig. 1i, wherein the re- .peating instrument is shown preferably at an intermediate station, the through connections being established by inserting the usual type of switch plug in its spring rjack 5l, said jack having the usual contact spring 52 herein shown as provided with an insulated contact plate 53 connected to one terminal 54 ofthe local. circuit, the other terminal .of said circuit being connected to a suitable contact 55 normally engaged by ttt said switch spring plate when the plug is removed. It will be observed from this arrangement that the insertion of the plugin its'jack elevates the contact spring and .breaks the local circuit7 thus stoppingthe the periodic anti packing` movement o microphone while the line is busy. l

ln Fig. 5` the local circuit leads to a. receiving station .and is connected with the switchhook upon which the receiver is normally hung when not in. use, the terminals of the local circuits beingl connected one to an insulated plate, 56, upon the usual spring controlled switch hook, 57, and the otheiito a suitable contact, 58, engaged by said plate, when the receiver is .hung up. in taking down the receiver, the switch hook is elevated by its spring and the local circuit is broken, so that the microphone is not turned during the use of the instrument.

Referring now to the modification of switch mechanism represented in Fig. 6, the

local circuit is provided with a spring controlled switch lever 6 0 pivotally and'sensitively mounted intermediate its ends upon a' suitable support 59. The right end of this switch lever normally rests upon the contact 61, to which one terminal of said. local circuitis attach ed,'the other being directly attached to said switch lever. lIhe contact end of this lever is also provided with a light spring arm 62, which normally acts to de- 'press the contact ofsaidv lever upon coop? :erating Contact, 61, thus maintaining thev circuit closed. The opposite end of this switch y lever is .provided with a suitable armature plate 63 beneath which is an electromagnet 64 in series with the main line circuit. By

this construction, it will be apparent` that when any current flows in the main line, the

electromagnet 64 will attract the vatmatured l end of said switch lever and depresses it thereby breaking-the local circuit in which the means for operating the antipacking device are located. lt is of course, understood that the current inv the main line is 0f an are relatively high in periodicity and the character or normal rate of vibration of the spring` 62 employed for maintaining the switch lever in circuit closing relationis not such as to permit of its yresponding to suoli a high rate of oscillation, so that the armatured end of the lever will be pulled down by .the electromagnet, to keepy the circuit open as long as the current flows in the main line circuit. Y

. While these three modifications, herein shown as illustrative of suitable means for alternating character but the alternations breaking the local circuit, diit'er in construction, one being under the control of an intermediate operator, who establishes through connection, the second under the control of the person who takes down the receiver at one of the talking stations, and the third ac I tuated. bythe voice caused' currents 01' the main line circuit,v it will be apparent that all are .made operative by the establishment of through coni'iections betweenthe talking stations thus providing effective means forl breaking the local circuit and preventing antipacking movement of the microphone while the line is in use. If desired, however, the switch mechanism may obviously be mitted and the intermittent action of the antipacking` mechcanism continued during the use of the line, so that there 'may be no effective packing` action of the carbon gram ules in the microphone during any extended use of the latter.

The circuit connection of the apparatus employed at the terminal stations being ot the usual construction, no description lneed be given except to say that the terminal stations are provided with receiving and transmitting instruments conventionally represented as in Fig. il, for example, as comprising the receiver G5, the transmitter G6, the latter being in local circuit with'a battery G7 and the primary winding of antinduction coil 65, a secondary of which is in series with the main line circuit and the receii er. n

ln Fig. 5, the circuit arrangement at but one circuit station is shown and issutlicient since that at the other terminal' is af mere du# plication thereof. In Fig. 64,. wl erein.. the switch mechanism ispreferably .at an intermediate repeating. or vrelaying station, the main circuit wires lead to the usfual terminal stations wherethe circuit connections (not shown) are the same as shown in Fig'. 1t.

In the telephone system shown in Fig. l, the operated circuit ot' the telephone rcpeating instrument is directly in .series with one side, (not the main line circuit4` so that the original voice actuated currents produce corresponding variations ot' magnetic action in the receiving magnet, which produces through actuation of the i'nicrophoi'ie, undulations in the repeating circuit harmonious and proportional to the original voice caused current undi'ilat'ions ot the main circuit. The current undulations in the repeating' circuit, c, through the action of the induction coil, 5, therein, are in turn induced upon the lnain line circuit, but in the pref-ent instance, upon the opposite side, Z), thereof, hence there is no direct or inductive relation be- -fective in the repeating instrument a ad is thereby transmitted 'to the main line.

lVhile in Fig. it the telephone repeating instrument and the operating and operated circuits thereof are in direct serial relation with the main line circuit, the operated circuit with one side and the operating circuit with the other, -niy `invention obviously not limited thereto, and compre bends placing-the operating' and operated circuits in inductive rclatiin'i lo the opposite sides o't` the main line as shown in Figi'.

'the current, and thus utilize the entire 7, but .in any event lserially, so as to avoid bridge ar angen'icnts and the .splitti'i'ig ol;

energy ot' the line. l

Referring to Fig. 7, the circuit arrangements' are but coiirentionally represented, and include' two Separate reinl'orcing circuits `each containing a repeating instrument ol." the type described, the two repeating circuits beiney reyersely arrz'inged between the sides ot' the n'n'iin line circuit and cach preferably cinistitutinpY a repcatinlgror rclaying;` station between the receiving or transmitting stations. ln the present in stance, what may be termed the imei-aline; circuit ot' the repeating instrument includes the receivingl n'iapgnet ifi, which is serially 'and inductively related to the main line and operated by the current vai'iaticns thereof to actuate the: current Varying mei ldiun'i or transmittingy element represented at 8'.- This current varying medium or transmitting clement. preferably herein ot the granular carbon type described, upon heine' actuated by the receiving magnet produces current undulalions in the repeatingr or opcralcd circuit o't' the instrument', which l term the operated circuit thereof nel only because it is operated by said reccivinii` magnet but because through induction coil in series with said` circuit, it induces oi' transmits io the main line circuit, the current undulalious proi'li'iccd therein in the rcpratiujr circuit which ai'c, as will be well understood, prol'iortional and hai'- mouions to thc original voice caused currcul uudulal'ions ot' said main line circuit.

ily invention provides a repeating or relaying' circuit and repeating' instruments that are ell'cclive to responi'l to impulses or cl'torts in every direction with equal sensitireness and without appreciable distortion ot thc reproduced sound. The construction ot' the clecli'omae'uet actuator and i'ui'- ci.-' pcratin;,; diaphragm ot the microphone eliminate. all wasteful mechanical ell'ort and accurc a direct magnetizing' ell'ort between them, so that, the pull ot' the niagnct, the diag'ih'iapjinatic pull and the resulting); ino\.'cuicnt olf the electrode are all coia-c'dcnt and :ict as :,'oiirdinalc actors to transmit magnetic uudulations primarily to the electrode and malte the latter delicately rcspoi'uirc thereto. lhe ell'ective action et the repeating' instrinnrnt and its delicato i'cspoi'isirencss to thc encre'izine,- current ol thil main line circuit would be inell'ective to produce the best results without the described n'ieans :for preventing the packing ol the granules in the carbon chamber, the arrangement Lt'or securing' this result maintaining' the instrument. in normal elliective condition al all times so that it is always ready 'tor instant use.

Where l reter to the repeater-receiver clcuicnt and the repealtir-transmitter element as being magnetically iiu'leiieudcnt each olE the oth-cr, l relier to 'freedom 'trom substantial. operative intcrlcrtau'e, and ordinarily (since. the coils necessarily have magnetic cores) a separation ot the magnetic cores ot the respective elements such that the magnetic llux set up bythe receivinn` instrument is not directly operative upon the transmitting' elem-eut, the latter heine' designed to be controlled by an indepcndcntly created magnetic llux.

llihile l' have described my invention with relation to one epccitic cmbi'ulimcnt thereot which has been selected i'or purposes 0l illustration herein. ily is to be iiinli\i.--'toi,id that my invention is not limited thereto, nor to thc spccilic details `o'l" construction and ariai1; \'ciiir-ntu but may be widely varied, and the numerous l'eatiires herein involved and which evidently possess novelty, may be employed either singly or without the re maining feature or features herein dis1 closed, Without departing from the spirit of my invention.

I claiml. A. current transmitting instrument,hav-

r net therein, a transmitting circuit., a granular microphone in said transmitting circuit having a vibratory electrode operatively related to and operated by said receiving magnet, and means for periodically disturbing saidmicrophone to maintain the granules in loose condition.

3. In a telephone system, a main line circuitl provided With terminal stationsI a current transmitting instrument therefor com prising a revoluble microphone provided with a vibratory electrode, a' fixed electrode and an intermediate body of granular carbon and means for intermittently producing rotary movement of said microphone to maintain the said carbon granules in unpacked condition, and means controlled by the establishment of through connections between talking stations of said main line circuit for preventing operation of said rotating means.

4. A telephone repeating instrument comprising a main line circuit, an electromagnet serially related thereto, a current varying microphone actuated thereby and also serially related to said line and provided with a fixed electrode, a vibratory electrode and a body of granular carbon intermediate said electrodes, means tor revolubly mount-' ing said microphone to maintain its vibratory electrode in magnetic operative relation to said magnet, means for intermittently rotating said microphone to maintain the said granules in unpacked condition, and means under the control of an operator for rendering said intermitting means inoperative. i

5. A telephone system having a relay provided-with a receiving magnet, a microphone actuated thereby provided ivit-h -a variable resistance medium, such as carbon granules, means for intermittently restoring said granules to their normally loose condition to prevent` packing thereof, and means rendered operative by the establishment of through connectionsbetween stations of sai-d system for rendering said restoringl means inoperative while the instrument is in use.

G. In a device of the type described', a.

granular carbon microphone, a rotary shaft to which said microphone is secured, means for revolubly supporting said shaft, an arm loosely mounted on said shaft and adapted to he clutched thereto for revolving saidy of said shaft upon oscillating said arm, and a local circuit and connected devices for intermittently oscillating said arm and revolving said shaft and said microphone.

8. In a telephone system, a main line circuit, a repeating instrument having an electromagnetic actuator inielectromagnetic relation to but one side of said main line circuit, and electromagnetic means, in noninductive relation to said actuator. in inductive relation with the .opposite side of said .line and operated by said actuator.

9. In a telephone system, a main line circuit, repeating circuit in electromagnetic relation to but one side of said main line circuit, said circuit containing a microphone and a source of electrical energy, and an' electromagnetic device operated by the current variations of said main line circuit and phone and-asource of electrical energy, an'

electromagnetic device operated by the current variations of said main line circuit andA in inductiverelation to the other side thereof for actuating said microphone and means for periodically agitating said microphone Vfor maintaining the carbon granules thereof in normal or unpacked condition.

11. In a telephone system the combination with a. main line circuit and terminal stations of an intermediate repeating station having a repeating circuit, an electromagnetically controlled microphone inthe same of the granular carbon type, and means independent of the condition ofthe carbon granules for automatically maintaining the same in unpacked condition.

12. In a telephone system, a main line circuit provided with terminal stations, an

'intermediate repeating station having a ree 'having a repeating circuit and a microphone ofthe granular carbon type, anti-packing meanst'or preventing the packing of the carbon` granules, and means for'controlling the operation of the anti-packing means by the discontinuance or resumption of service' on the mainline.

14. In a telephone system, the combination with a main line circuit and terminal stations of an intermediate repeating statio-n having a repeating circuit and an electromagnetically controlled, solid-back microphone in the same, and means for automatically moving the microphone to maintain the carbon granules in unpacked condition.

.15. The combination with a telephone line having a 2-Way metallic circuit, of a repeating apparatus provided with magnetically independent receiving and transmitting elements, operatively related to each other, the

operating circuit of the receiving element being in series relation Vto one side only oi themain line circuit and the operated circuit of the transmitting Velement bein(r in series relation to the other side only ot the vsaid main line circuit.

16. In a telephone system, 1n combination with a metallic circuit, current reinforcing instrumentalitics comprising magnetically independent receiving and transmitting elements, the former operatively relatedto the latter; the said receiving element being serially related to one'v side only of said circuit and the said transmitting element being serially related tothe other side only ot said circuit.

17. In atelephone system, in combination `with al metallic circuit, current reinforcing instrnmentalities comprising a pair ot' symmetrically placed reinforcing devices, each comprising a receiving and a translnitting element that are operatively related the first to the second and are magnetically independent, a receiving element, ot' one and a transmitting element ofthe other of the pail being serially and magnetically independently related to each side of said circuit,

said elements being cach serially related tov oneside only of the main line circuit.

1S. In a tclcplnme system, in combination with a metallic circuit, current reinforcing instrumentalitics comprising receiving and transmitting elements, the 'former operatively related to the latter; the said receiving element being serially related to one side -only or' Asaid circuit and the said transmitting element beingserially related to the other side only of said circuit.

19. In a telephone system, the combination with a transmitting and a receiving device and an intermediate continuous main line circuit of a repeating circuit, means serially associated with one' side only of the main line circuit for producing current variations in the repeating circuit to correspond to energy variations in the telephone circuit and means inductively related to the repeating circuit but not inductively associated with the current-variation-prodncing means for reinforcing the energy passing through the said current-variation-produc-` ing means, said reinforcing means being se rially related to the other side only of the main line circuit.

20. In a telephone system, in combination with a transmitting and a receiving device and a continuous main circuit line between the same, of a` repeating circuit inductivcly related to one side only thereof, a current varying medium associated with said repeating circuit, and means serially ,associated with the other side only opt the said line circuit to actuate said current-varying me-V dium for lreproducing current undulations over the line circuit in the repeating circuit.

21. In a telephone repeating system, the combination witha main line metallic circuit et' .transmitting and receiving apparatus at the terminals thereof; a repeater intermediate said terminals having a coil in series with one side o't said circuit; a local battery and coil associated with said repeate'; and a third coil in inductive relation with said second mentioned coil and in series with the other side o't' "aid circuit, substantially as described.

In testimony whereof, lIliave signed my name to" thisspecification, in the presence ot' two subscribing Witnesses.

CHARLES D. LANNING.

Vitncssesz h Amon RICHMOND BROWN, AGNES B. Henson. 

